Miyajima H, Takahashi Y, Suzuki M, Shimizu T, Kaneko E
First Department of Medicine, Hamamatsu University School of Medicine, Japan.
Neurology. 1993 Jul;43(7):1414-9. doi: 10.1212/wnl.43.7.1414.
Recurrent rhabdomyolysis due to decreased glycolysis occurred during strenuous exercise in patients with lactate dehydrogenase-A-subunit (LDH-A; muscle) deficiency. Enzyme activities of LDH in the muscle were decreased less than 8% of the control value. The isozyme pattern revealed only one band of B4. The level of LDH-A mRNA was not decreased. The direct sequencing of the reverse transcription-polymerase chain reaction product that corresponds to exon 6 revealed a deletion of 20 nucleotides. Immunofluorescence staining showed the presence of LDH-A protein within the cytoplasm. These findings suggest that an incomplete LDH-A protein lacking the subunit contact subdomain could not assemble into a tetrameric structure that has an enzymatic activity.
乳酸脱氢酶A亚基（LDH-A；肌肉型）缺乏的患者在剧烈运动期间，因糖酵解减少而发生复发性横纹肌溶解。肌肉中LDH的酶活性降低至对照值的8%以下。同工酶谱仅显示一条B4带。LDH-A mRNA水平未降低。对对应于外显子6的逆转录-聚合酶链反应产物进行直接测序，发现有20个核苷酸的缺失。免疫荧光染色显示细胞质内存在LDH-A蛋白。这些发现表明，缺乏亚基接触亚结构域的不完整LDH-A蛋白无法组装成具有酶活性的四聚体结构。
